His Dark Materials author Philip Pullman is heading a new charge from writers demanding to be rewarded fairly for their work, as the Society of Authors warns that unless “serious” changes are made by publishers, the professional author “will become an endangered species”.

In an open letter to Britain’s publishers, the Society of Authors points to a recent survey that found that the median income of a professional author is now just £11,000, with only 11.5% of UK writers making a living solely from writing.

Pointing out that “authors remain the only essential part of the creation of a book and it is in everyone’s interests to ensure they can make a living”, it tells publishers that “unfair contract terms, including reduced royalty rates, are a major part of the problem”.

Pullman, the current president of the society, said that the case for fair terms for writers was “overwhelming”.

“From our positions as individual creators, whether of fiction or non-fiction, we authors see a landscape occupied by several large interests, some of them gathering profits in the billions, some of them displaying a questionable attitude to paying tax, some of them colonising the internet with projects whose reach is limitless and whose attitude to creators’ rights is roughly that of the steamroller to the ant,” said Pullman.

“It’s a daunting landscape, far more savage and hostile to the author than any we’ve seen before. But one thing hasn’t changed, which is the ignored, unacknowledged, but complete dependence of those great interests on us and on our talents and on the work we do in the quiet of our solitude. They have enormous financial and political power, but no creative power whatsoever. Whether we’re poets, historians, writers of cookery books, novelists, travel writers, that comes from us alone. We originate the material they exploit.”

The society wants authors to receive at least 50% of ebook revenue, rather than 25%, and is also asking publishers not to discriminate against writers “who don’t have powerful agents”.

“Some publishers are excellent but we see many inequitable contracts. Without serious contract reform, the professional author will become an endangered species and publishers – as well as society at large – will be left with less and less quality content,” says the letter, sent by Society of Authors’ chief executive Nicola Solomon.

“Unless publishers treat their authors more equitably the decline in the number of full-time writers could have serious implications for the breadth and quality of content that drives the economic success and cultural reputation of our creative industries in the UK.”

All writers want, said Pullman, “is fairness”. “We don’t want these great powers to disappear altogether: the things they do are often things that need doing. Books are physical objects that need to be manufactured and transported and sold, or digital entities that need to be formatted and made available online. Sometimes there are things we wish they would do a little more of: editorial standards are not what they were. All those things are necessary and should be rewarded – but rewarded fairly. So is our work, and so should we,” said the novelist.